Cytogenetic damage related to low levels of methyl mercury contamination in the Brazilian Amazon

Abstract

The mercury rejected in the water system, from mining operations and lixiviation of soils after deforestation, is considered to be the main contributors to the contamination of the ecosystem in the Amazon Basin. The objectives of the present study were to examine cytogenetic functions in peripheral lymphocytes within a population living on the banks of the Tapajós River with respect to methylmercury (MeHg) contamination, using hair mercury as a biological indicator of exposure. Our investigation shows a clear relation between methylmercury contamination and cytogenetic damage in lymphocytes at levels well below 50 micrograms/gram, the level at which initial clinical signs and symptoms of mercury poisoning occur. The first apparent biological effect with increasing MeHg hair level was the impairment of lymphocyte proliferation measured as mitotic index (MI). The relation between mercury concentration in hair and MI suggests that this parameter, an indicator of changes in lymphocytes and their ability to respond to culture conditions, may be an early marker of cytotoxicity and genotoxicity in humans and should be taken into account in the preliminary evaluation of the risks to populations exposed in vivo. This is the first report showing clear cytotoxic effects of long-term exposure to MeHg. Although the results strongly suggest that, under the conditions examined here, MeHg is both a spindle poison and a clastogen, the biological significance of these observations are as yet unknown. A long-term follow-up of these subjects should be undertaken.

Daily mercury intake in fish-eating populations in the Brazilian Amazon

“…In these populations, there is strong evidence of early nervous system dysfunction and, to a less extent, immunologic and cardiovascular effects among both adults and children (Lebel et al, 1996(Lebel et al, , 1998Grandjean et al, 1999;Amorim et al, 2000;Dolbec et al, 2000;Harada et al, 2001;Cordier et al, 2002;Mergler, 2002;Yokoo et al, 2003;Silbergeld et al, 2005;Fillion et al, 2006).…”

Chercheurs d'or et contamination par le mercure des systèmes aquatiques continentaux de Guyane – Risques à l'égard des populations humaines

“…Les déficits observés sont similaires à ceux décrits au Brésil, qui montrent des dysfonctionnements au niveau de la coordination et de la rapidité des mouvements fins, avec une diminution de sensibilité aux contrastes visuels (Dolbec et al, 2000 ;Grandjean et al, 1999 ;Lebel et al, 1996). Des effets cytogénétiques, à partir de la détermi-nation de l'index mitotique sur des globules blancs, ont été récemment mis en évidence sur des populations brési-liennes des rives du Tapajos, les effets étant une nouvelle fois fortement corrélés aux teneurs en Hg dans les cheveux (Amorim et al, 2000).…”

Estratégias metaloproteômicas na investigação de biomarcadores de mercúrio em amostras de tecido muscular de tucunarés

“…Segundo Amorim et al (2000) e Roulet et al (1998) A distribuição da massa de mercúrio total em função do comprimento aumentam na sequência: rio Madeira < reservatório da UHE Cana Brava < reservatório da UHE Balbina < rio Purus < reservatório da UHE Tucuruí < rio Solimões < rio Apuaú < rio Negro. Considerando as características físico-químicas de cada ambiente, os ambientes de águas escuras possuem as maiores massas de mercúrio neste estudo.…”

“…É importante destacar que a construção de grandes empreendimentos hidrelétricos é um dos vários fatores que influenciam a dinâmica hidrobiogeoquímica natural do mercúrio no ambiente, visto que, a construção de reservatórios artificiais formam microambientes lênticos que podem maximizar o processo de organificação do mercúrio e solubilizar outras substâncias tóxicas (AMORIM et al, 2000;ROULET et al, 1998).…”

“…Uma ótima ferramenta de biomonitoramento são os biomarcadores, os quais são instrumentos que possibilitam identificar a substância tóxica ou uma condição adversa antes que sejam evidenciados danos à saúde. Os biomarcadores podem ser classificados em três tipos: de exposição, de efeito e de suscetibilidade (AMORIM, 2003).…”